AP BIOLOGY

Detailed explanation-1: -When you exercise and your muscles work harder, your body uses more oxygen and produces more carbon dioxide. To cope with this extra demand, your breathing has to increase from about 15 times a minute (12 litres of air) when you are resting, up to about 40–60 times a minute (100 litres of air) during exercise.

Detailed explanation-2: -When you exercise, your muscles move more vigorously than when you are at rest. Their metabolic rate increases. They need more energy, so they produce more of the chemical energy molecule ATP. You need oxygen to produce ATP, so the more ATP you produce, the more oxygen your body requires.

Detailed explanation-3: -Oxygen is then carried to the muscles via red blood cells. And whether you’re exercising or not, the oxygen in your body is used to break down glucose, creating fuel for your muscles–that is, adenosine triphosphate, or ATP. This molecule is the source of energy that keeps your entire body going at all times.

Detailed explanation-4: -Muscles performing work require increasing amounts of energy as the workload increases, which correspondingly requires more and more oxygen.